Dielectric thin films have applications in semiconductor memory devices, such as dynamic random access memory, DRAM, devices and in wireless communication systems. Important characteristics for these applications include low dielectric losses (tan δ) and high dielectric constants (κ). The operating frequencies for devices using these dielectric thin films extend not only to hundreds of megahertz, MHz, but to tens of gigahertz, GHz. As a result, dielectric materials useful for increased scaling in microelectronic devices such as semiconductor memories need to provide low loss characteristics at GHz operating frequencies.
Currently, the semiconductor industry relies on the ability to reduce or scale the dimensions of its basic devices, primarily, the silicon based metal-oxide-semiconductor field effect transistor (MOSFET). A common configuration of such a transistor is shown in FIG. 1. While the following discussion uses FIG. 1 to illustrate a transistor from the prior art, one skilled in the art will recognize that the present invention could be incorporated into the transistor shown in FIG. 1 to form a transistor according to the present invention. A transistor 100 is fabricated in a substrate 110 that is typically silicon, but could be fabricated from other semiconductor materials as well. Transistor 100 has a source region 120 and a drain region 130. A body region 132 is located between source region 120 and drain region 130, where body region 132 defines a channel of the transistor with a channel length 134. A gate dielectric 140 is located on body region 132 with a gate 150 located over gate dielectric 140. Although gate dielectric 140 may be formed from materials other than oxides, gate dielectric 140 is typically an oxide, and is commonly referred to as a gate oxide. Gate 150 may be fabricated from polycrystalline silicon (polysilicon), or other conducting materials such as metal may be used.
In fabricating transistors to be smaller in size and reliably operate on lower power supplies, one design criteria is gate dielectric 140. The mainstay for forming the gate dielectric has been silicon dioxide, SiO2. A thermally grown amorphous SiO2 layer provides an electrically and thermodynamically stable material, where the interface of the SiO2 layer with underlying Si provides a high quality interface as well as superior electrical isolation properties. However, increased scaling and other requirements in microelectronic devices have created the need to use other dielectric materials as gate dielectrics.